Disc-type parking brakes utilizing sliding calipers are known in the prior art. Such parking brakes generally include a caliper body slidably mounted on a pair of parallel pins affixed to the vehicle suspension. Such a mounting allows the caliper body to slide back and forth a short distance parallel to the axis of rotation of the wheel. The caliper body has a slot-shaped recess that receives the outer periphery of a brake rotor. On one side of the recess, the caliper body includes a pair of cylindrical bores that house a pair of spring-loaded brake pistons. These pistons are connected to an inner brake pad that is extendible toward and retractable away from the brake rotor. An outer brake pad is connected to the caliper body on the outer wall of the rotor-receiving recess opposite to the inner brake pad such that the outer periphery of the brake rotor is disposed between the inner and outer brake pads.
When the vehicle is in operation, the brake pistons are retracted against the force of their internally-contained springs by pressurized brake fluid acting against the front ends of the pistons. When the vehicle is stopped and the parking brake is actuated, the pressurized brake fluid is released from the bores housing the pistons, which allows the piston springs to extend the pistons toward the brake rotor. The extended brake pistons forcefully engage the inner brake pad against the inner surface of the brake rotor. This engagement force reacts against the slidably mounted caliper body, causing it to slide on the mounting pins a small distance away from the rotor, thereby pulling the outer brake pad (which is connected to the caliper body on the outer wall of the rotor-receiving recess) into engagement against the outer surface of the brake rotor. To release the parking brake, pressurized brake fluid is re-admitted into the front ends of the cylindrical recesses in the caliper body. The resulting hydraulic force pushes against the front face of the brake pistons against the force of their internally-contained springs, thereby retracting the pistons and the inner brake pad from the brake rotor. The outer pad separates from the brake rotor disc as a result of the “knock back” force the rotor applies against the outer pad when the inner brake pad is released and the rotor rotates.
Such sliding caliper parking brakes have a number of advantages. The ability of the caliper body to slide in the axial direction upon the actuation of the brake allows the brake pistons to be mounted on only one side of the caliper body, thereby simplifying construction, reducing parts and reducing the size and weight of the brake. The use of spring force instead of hydraulic force to extend the brake pistons allows the parking brake to reliably apply a braking force against the brake rotor without power from the vehicle, and regardless of whether pressurized brake fluid is available or leaks out of the piston bores of the caliper body.